Does a continuous effect that sets power and toughness override a pump spell cast earlier?

Magic resolves power/toughness modifications in a structured system called the layer system, specifically within Layer 7 (CR 613.3). Layer 7 is divided into sublayers: 7a (characteristic-defining abilities), 7b (effects that set P/T to specific values), 7c (effects that modify P/T, like +X/+X), and 7d (effects that switch P/T).

A 'pump spell' such as Giant Growth (+3/+3) creates a Layer 7c effect. A continuous effect that sets P/T to specific values (e.g., Humility making all creatures 1/1, or Quicksilver Elemental's ability) creates a Layer 7b effect. Because 7b is always applied before 7c regardless of timestamps, the set-P/T effect lays the foundation and then the pump is applied on top — not the other way around (CR 613.3b, 613.3c).

This means the pump spell is NOT overridden in most cases — it still adds its bonus on top of the set value. For example, if Humility (sets all creatures to 1/1) is in play and you cast Giant Growth on your creature, the creature becomes 4/4: Humility sets it to 1/1 (layer 7b), then Giant Growth adds +3/+3 (layer 7c).

However, if the continuous effect sets P/T in layer 7b and was applied after another 7b effect, timestamp order matters within the same sublayer (CR 613.7). But pump spells (+X/+X) live in 7c and are always applied after any 7b setter, so they always contribute their bonus on top.

The only scenario where a 'set' effect truly overrides a pump is if both effects operate in the same sublayer (both set P/T, i.e., both are 7b), in which case the later timestamp wins (CR 613.7a).